Add isort in pre commit configuration file

[Pierre-Sassoulas]

Description

This add isort in the pre-commit configuration file and also apply it on all applicable files. Isort permit to sort import so there is less conflict during merging and rebase of file with conflicting modification. We're using a style of import compatible with black and made some efforts so that automated changes made by black are not deemed invalid and automatically reverted by isort later in the commit hooks :

• The ignored file are the same
• The line length is the same
• The style of import is compatible (For more detail see Wrapping imports is incompatible with isort psf/black#127)
• For comment inside import, there is a minor issue that would require a change in Black : isort removes newlines before standalone comments if the following line is an import of the same group psf/black#251

It also update the version of Black, and of pre-commit's trailing-whitespace and end-of-file-fixer

Type of Changes

| ✓ | 🔨 Refactoring |

[Pierre-Sassoulas]

I moved a comment from the import to the top of the file in pylint/test/conftest.py because isort and black are not entirely compatible yet. (IMHO its compatible enough if the only problem is on one file for the entire project.). See this issue : psf/black#251

[coveralls]

Coverage decreased (-0.03%) to 89.716% when pulling da9c49b on Pierre-Sassoulas:add-isort-in-pre-commit into 5073ebd on PyCQA:master.

[coveralls]

Coverage decreased (-0.03%) to 89.716% when pulling da9c49b on Pierre-Sassoulas:add-isort-in-pre-commit into 5073ebd on PyCQA:master.

[coveralls]

Coverage decreased (-0.03%) to 89.701% when pulling 09913f1 on Pierre-Sassoulas:add-isort-in-pre-commit into 8d2f5d0 on PyCQA:master.

[Pierre-Sassoulas]

#2806 might be blocking.

[PCManticore]

Great stuff @Pierre-Sassoulas ! Thank you for working on this. The next steps would be to have isort in CI as well, once that's in we can merge this.